DeSoto Custom: Which Version Should You Choose?
The DeSoto Custom Cabrio was produced from 1949 to 1952 in the listed 2 generation, with two versions: 3.9 AT and 4.1 AT. Both use a naturally aspirated, carbureted Inline 6 Gasoline engine, a 4-speed Automatic gearbox, and RWD.
The DeSoto Custom Cabrio was produced from 1949 to 1952 in the listed 2 generation, with two versions: 3.9 AT and 4.1 AT. Both use a naturally aspirated, carbureted Inline 6 Gasoline engine, a 4-speed Automatic gearbox, and RWD. The main buying decision is therefore not about body style, transmission, or drivetrain; it is about whether the 4.1 AT’s additional output justifies its extra kerb weight. On the available figures, the 4.1 AT is the stronger choice, while the 3.9 AT offers slightly better power-to-weight and power-per-litre ratios.
Generation comparison
Only one generation is represented in the supplied catalogue data: 2 generation, produced from 1949 to 1952. It has a Cabrio body and two versions, 3.9 AT and 4.1 AT. Because no other generation or restyling is included, there is no supported basis for claiming that another generation changed the engine range, design, dimensions, equipment, reliability, or driving characteristics.
Within 2 generation, the 3.9 AT and 4.1 AT share the same basic mechanical format. Each has a front, longitudinal Gasoline engine with 6 cylinders in an Inline layout, 2 valves per cylinder, no boost, carburetor fuel delivery, a compression ratio of 7, a 4-speed Automatic gearbox, and RWD. Both versions also have independent, spring front suspension; dependent, leaf spring rear suspension; and Drum brakes at the front and rear.
Engine specs and version comparison
| Version | Displacement | Power | Torque | Fuel | Cylinders and layout | Boost | Gearbox | Drive |
|---|---|---|---|---|---|---|---|---|
| 3.9 AT | 3,878 cc | 114 hp (84 kW) at 3,600 rpm | 264 Nm at 1,600 rpm | Gasoline | 6, Inline | No | 4-speed Automatic | RWD |
| 4.1 AT | 4,106 cc | 118 hp (87 kW) at 3,600 rpm | 282 Nm at 1,600 rpm | Gasoline | 6, Inline | No | 4-speed Automatic | RWD |
The 4.1 AT has 228 cc more displacement than the 3.9 AT. That increase brings 4 hp, 3 kW, and 18 Nm more output. In percentage terms, the 4.1 AT has about 5.9% more displacement, 3.5% more horsepower, and 6.8% more torque. Both engines reach maximum power at 3,600 rpm and maximum torque at 1,600 rpm, so the larger version’s advantage is additional output at the same stated engine speeds.
The bore is 87.3 mm in both versions. Stroke is 107.95 mm in the 3.9 AT and 114.3 mm in the 4.1 AT, a difference of 6.35 mm. The available data therefore distinguishes the engines through displacement, stroke, power, torque, and weight rather than through cylinder count, layout, aspiration, fuel system, or compression ratio.
Calculated specific output slightly favors the smaller engine. The 3.9 AT produces about 29.4 hp per litre and 68.1 Nm per litre, while the 4.1 AT produces about 28.7 hp per litre and 68.7 Nm per litre. In practical catalogue terms, the 3.9 AT delivers marginally more horsepower from each litre, whereas the 4.1 AT delivers marginally more torque from each litre.
Performance, mpg, and fuel economy
Acceleration from 0–100 km/h is not measured for the 3.9 AT and not measured for the 4.1 AT. Top speed is also not measured for either version. Consequently, the extra 4 hp and 18 Nm of the 4.1 AT cannot be translated into a verified acceleration or maximum-speed advantage.
City fuel consumption is not measured for both versions. Highway fuel consumption is not measured, and combined fuel consumption is not measured as well. MPG therefore cannot be calculated reliably from the supplied information. CO₂ emissions and environmental class are also not measured for both versions.
Each version has a 64-litre fuel tank. Since the tank capacity is identical and fuel consumption is not measured, no evidence-based range comparison can be made between the 3.9 AT and 4.1 AT.
Dimensions, weight, and chassis specs
Full exterior dimensions are not measured for either version. Ground clearance is not measured, and wheel sizes are not measured. Gross weight is also not measured for both the 3.9 AT and 4.1 AT.
Kerb weight is available: the 3.9 AT weighs 1,730 kg, while the 4.1 AT weighs 1,750 kg. The 4.1 AT is therefore 20 kg heavier, an increase of about 1.2%.
The calculated weight-to-power figures are close. The 3.9 AT carries about 15.18 kg per hp, compared with about 14.83 kg per hp for the 4.1 AT. Expressed as power per tonne, that is about 65.9 hp per tonne for the 3.9 AT and 67.4 hp per tonne for the 4.1 AT. The larger version’s extra output more than offsets its additional kerb weight on this calculation.
The weight-to-torque comparison favors the 4.1 AT more clearly. The 3.9 AT has about 6.55 kg per Nm, while the 4.1 AT has about 6.21 kg per Nm. This does not establish measured road performance, but it shows that the 4.1 AT combines the better torque figure with the better torque-to-weight ratio.
Both versions use the same listed suspension and braking specifications: independent, spring suspension at the front; dependent, leaf spring suspension at the rear; and Drum brakes on both axles. There is therefore no data-supported chassis or brake advantage for either version.
Reliability and problems
Reliability data is not measured for the 3.9 AT and not measured for the 4.1 AT. Recorded problems, failure rates, maintenance costs, and component life are likewise not measured. The shared engine layout, carburetor system, transmission type, drivetrain, suspension descriptions, and brake type do not prove that the two versions have equal reliability.
A purchase decision based on reliability cannot be made from these specifications alone. The available data supports a comparison of output, displacement, kerb weight, and mechanical layout, but it does not support claims that either version is more durable or less troublesome.
Which DeSoto Custom version should you buy?
Choose the 4.1 AT if the priority is the strongest specification available in this DeSoto Custom generation. Compared with the 3.9 AT, it provides 4 hp more power and 18 Nm more torque for an additional 20 kg of kerb weight. It also has the better calculated power-to-weight ratio at about 67.4 hp per tonne and the better weight-to-torque ratio at about 6.21 kg per Nm.
Choose the 3.9 AT if the priority is the lighter version or slightly higher horsepower per litre. It weighs 1,730 kg—20 kg less than the 4.1 AT—and produces about 29.4 hp per litre rather than about 28.7 hp per litre. It otherwise retains the same listed 4-speed Automatic gearbox, RWD, 64-litre tank, suspension types, and Drum brakes.
Price data is not provided, so the extra cost of the 4.1 AT and the value of that premium cannot be measured. What its larger engine buys in specification terms is clear: 228 cc more displacement, 4 hp more power, and 18 Nm more torque, accompanied by 20 kg more kerb weight. Without price, fuel-consumption, performance, or reliability measurements, the 4.1 AT is the numerical choice for greater output, while the 3.9 AT is the numerical choice for lower weight and marginally better horsepower per litre.